linux-kernel - Re: [PATCH 1/1] hugetlbfs: handle pages higher order than MAX

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48ECDD37.8050506@linux-foundation.org>
Date:	Wed, 08 Oct 2008 11:17:59 -0500
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Andy Whitcroft <apw@...dowen.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Jon Tollefson <kniht@...ux.vnet.ibm.com>,
	Mel Gorman <mel@....ul.ie>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [PATCH 1/1] hugetlbfs: handle pages higher order than MAX_ORDER

Andy Whitcroft wrote:
> When working with hugepages, hugetlbfs assumes that those hugepages
> are smaller than MAX_ORDER.  Specifically it assumes that the mem_map
> is contigious and uses that to optimise access to the elements of the
> mem_map that represent the hugepage.  Gigantic pages (such as 16GB pages
> on powerpc) by definition are of greater order than MAX_ORDER (larger
> than MAX_ORDER_NR_PAGES in size).  This means that we can no longer make
> use of the buddy alloctor guarentees for the contiguity of the mem_map,
> which ensures that the mem_map is at least contigious for maximmally
> aligned areas of MAX_ORDER_NR_PAGES pages.

But the memmap is contiguous in most cases. FLATMEM, VMEMMAP etc. Its only
some special sparsemem configurations that couldhave the issue because they
break up the vmemmap. x86_64 uses VMEMMAP by default. Is this for i386?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/